A federal report released yesterday lays the majority of blame for the 2010 Deepwater Horizon explosion and oil spill squarely on BP, although the report's authors said the actions of several other companies contributed to the disaster.

Eleven workers were killed in the blast, which unleashed approximately 200 million gallons of crude oil into the Gulf of Mexico -- the worst offshore oil spill in U.S. history.

In the report, BP was criticized for violating federal regulations, making last minute changes to plans, failing to observe and respond to critical indicators, lacking adequate well control response and failing to train its personnel in emergency bridge response.

The joint investigation by the Bureau of Ocean Energy Management Regulation and Enforcement (BOEMRE) and the U.S. Coast Guard determined that the blowout was caused by the failure of a cement barrier in the production casing string, a high strength steel pipe set in a well to ensure well integrity and to allow future production. The barrier failed to allow hydrocarbons to flow up the wellbore, through the riser and onto the rig, resulting in the deadly blowout. BP contractor Haliburton performed the cement work and was supposed to monitor the well.

In addition to Haliburton, other companies named in the report include Deepwater Horizon owner Transocean, which bypassed alarms and automatic shutdown systems and Cameron, which designed the Deepwater Horizon blowout preventer stack.

The report echoed findings of previous investigations but assessed more of the blame to BP, the designated operator of the well. The company is expected to face criminal charges and billions of dollars in fines for its role in the disaster.

The BOEMRE said that in the wake of the Deepwater Horizon tragedy, it launched “aggressive and comprehensive reforms” to offshore oil and gas regulation and oversight. The reforms strengthen requirements for everything from well design and workplace safety to corporate accountability. An additional rule, which will be made available for public comment in the coming weeks, will incorporate additional safety requirements that are related to the findings of the investigation.

Despite this, Congress has failed to pass any legislation to address the failures that led to the disaster. Republican lawmakers have dragged their feet on reforms, citing the need for this latest federal investigation to be completed.